Steam generator with dust separator



30; 1952 w. H. ARMACOST STEAM GENERATOR WITH DUST SEPARATOR 2SHEETS-SHEET 1 Filed Feb. 26. 1947 g Q 0 J 0 0G 0 o o o 2 2 um@@ 9 2@@Q@@@@ "IAIHHHHHHHIIIHMII a M m OOOOOOOOOOOOOOOOOGOO B WM 0 n M n a L 21 m A F M 00000 OOOOOOOOOOOOOOOO/ 7 7 ucost w- INVENTOR. ur H. Aim

M I O 2 M C 5 T T a. 7 E N m 3 E N l 2 S 8 9 W 6 E S 3 3 D I H 2 m a f mwo o o o Mo 0 w S w n N w J W 2 m m m m P o a o o o U w M] m o M 0 M w on w w n c m Y 0 0 0 0 0 0 0 0 B A 5 I I L E /l\ W. H. ARMACOST STEAMGENERATOR WITH DUST SEPARATOR Dec. 30, 1952 Filed Feb. 26, 1947 PatentedDec. 39, 1952 STEAM GENERATOR WITH DUST sEPARAToB.

Wilbur H. Armacost, Scarsdale, N. Y., assignor, by

mesne assignments, to Combustion Engineering-Superheater, 1110., acorporation of Delaware Application February 26, 1947, Serial No.731,086

2 Claims.

This invention relates to improvements in steam generators and inparticular to an improved organization of the elements of a steamgenerating unit and dust separator.

The usual arrangement of the elements of steam generating units, withrespect to the flow of products of combustion leaving the furnace,comprises a. furnace followed by heat absorbing surfaces including: someboiler surface serving as a screen for superheater surface, saidsuperhea-ter surface, boiler convection surface, economizer surfaceand/or air heater surface. Whenever dust separators have been used toremove the fly ash from the flue gases these have generally been placedafter the air heater and ahead of the induced draft fan with respect tothe gas flow.

When burning certain fuels in a furnace, such as anthracite, it has beenfound that the fly ash or dust carried by the flue gases flowing throughthe steam generating unit causes objectionable abrasion of the heatabsorbing surfaces and particularly abrasion of the air heater surface.To overcome this objection it has been proposed to locate the dustseparator between the main bank of boiler convection surface and the airheater or the economizer, if present, to thereby effectively reduce theabrasion of the air heater and economizer surfaces by deliveringdust-free flue gases thereto from the separator.

Furthermore, in the flow of gases through the various elements of thesteam generating unit there may be unequal rates of mass flow for (lifferent portions of the gases over the width of the heating surfaces dueto unequal resistance in the flow paths of said different portions. Suchunequal rates of flow will in turn cause unequal amounts of heat to beabsorbed from the gases by the heat absorbing surfaces over said widthresulting in a reduction of the average heat absorption by the apparatusat a given rating of the unit.

In large steam generating units there has been a recent tendency to havethe passes through which the furnace gases flow across the heatingsurfaces of such proportions that the velocity of the gases therethroughare relatively low, result ing in lower resistances through said. passesand a consequent relatively lower power requirement to move the gasesthrough the unit. Such lower resistances will increase the tendency tosaid un equal rates of gas flow because said unequal resistances will bea proportionately greater influence on the gas fiow compared to thelower total resistance through the unit.

It is an object of this invention to provide an improved arrangement ofdust separator in a steam genera-ting unit to reduce abrasion of a largeportion of th elements of heating, surface thereof while. providing bysaid novel arrange furnace A, boiler heating surf-ace B, a superheaterC, a dust separator D and a heat exchanger 131.. As shown in Figure 1fuel may be burnedfwithin the furnace as for example by a spreader.stoker F which delivers the fuel onto a traveling gr-ateG.

Referring to Figures 1 and 2, the furnace A comprises front wall I, sidewalls 2 and a roof 3 all of which may be faced with cooling tubes 4,

as shown on the front wall and roof. connected into the watercirculation of the boiler. The rear furnace wall -5 is formed by abafiie S mounted on the front row 9 of boiler tubes.

The boiler B proper comprises a lower water drum 1 and .an upper steamand water drum 8 into which the front row 9 of boiler tubes connect. Asecond row of boiler tubes it! and abank of boiler tubes H connect into.the top and bottom drums B and l as shown. The front iow of boiler tubes9 extends from the lower drum l in transverse parallel arrangementupwardly to Within a distance from the roof whence every alternate tubeis bent forwardly into the furnace to thereby be spaced from theremaining tubes and all of the tubes thus spaced extend upwardly intothe upper drum 8. In this manner open lanes are provided between tubesthrough whi-chthe gaseous products of combustion from furnaceA pass.Bafiling E, which forms the rear wall of no furnace and is mounted onthe front row of tubes 9, extends from the bottom drum 7 upwardly to thepoint at which the tubes are bent apart.

Mounted on the second row of boiler tubes I0 is bame l2 the top andbottom ends of said baffle being spaced from the top and bottom boilerdrums 8 and 1 to provide passages therebetween for the gases. Mounted onthe front row of the bank of boiler tubes I I is baffle I3 which extendsfrom the upper drum 8 downwardly and has its bottom end spaced from thelower drum 1 to provide a passage L therebetween for the gases. Thebottom Ma of battle I3 continues transversely across the bank of boilertubes H in a generally downward direction and joins the top tube sheet[6 of dust separator D. Bafile I ia divides tube bank H into twoportions, a smaller lower portion V and a substantially larger upperportion W. The smaller portion V in exposing to the gases a relativelysmall section of the boiler heating surface is so proportioned that thevelocity of the gases is held relatively low, i. e., in the neighborhoodof 40 ft. per second. The larger portion W of tube bank I I on the otherhand presents to the gases the major portion of the boiler heatingsurface, over which the gases are made to flow following a sinuous pathdefined by cross baffles 13a, which confine the gases to a channelhaving a considerably smaller flow area than that presented to the gasesby the lower tube bank portion V, said sinuous channel being soproportioned that the velocity of the gases flowing over the major tubebank portion W will be in the neighborhood of 65 ft. per second. Apartition wall l5 spaced rearwardly from the bank of boiler tubes E lforms the rear wall of the gas pass through the bank of'boiler tubes.The

tending upwardly through top tube sheet I4 into which it is fastened,and with a dust outlet 34 discharging into hopper 2|. Between the wallsof each cyclone 32 and the clean gas offtake 33 there are provided amultiplicity of circumferentially arranged gas deflecting vanes 35(again see Figure 2). These vanes 35 receive the dust Lladen gas comingfrom the bottom portion of the bank of boiler tubes I and direct it to awhirl into the cyclone 32. The separated dust flows downwardly intohopper 2| while the clean gas flows upwardly through offtake 33 andthence into the upper portion of the tube bank H.

Figure '3 is similar in arrangement to Figure l excepting that the bankof boiler tubes shown in Figure 1 is omitted and that an additionalsection of superheater tubes SE is placed on the furnace side of bafiie6' while a still further group of superheater tubes S is shown asfollowing the dust collector D. A row of spaced boiler tubes .31

- extends into the furnace ahead of said superbottom of partition l5j0i1ls the top wall N5 of dust separator D.

A hopper I? has a front wall 18 extending downwardly from the rear oflower drum land a rear wall l9 extending downwardly from the bottom tubesheet .29 of dust separator D. The side walls 2 of the furnace extendrearwardly to partition l5 and form a seal with the ends of bafiles 5,,I2, 13 and partition Dust separator D is provided with a dust collectinghopper 2|.

. Above dust separator D is located a heat exchanger E which in thisinstance is shown as an air heater having a bank of gas conducting tubes22 fastened into top and bottom tube sheets 23 and 24 and is enclosed byan air chamber defined by rear plate 25, partition l5 and side plates 26all of which make sealed connections with each other at their meetingedges and with the top and bottom tube sheets 23 and 24. An air intake2] is provided at the top of the air chamber in plate and air ofitakeconnections 28 are provided .at the bottom of the air chamber in plates26. Partitions 27a. and 28a extend across the tube bank 22 and guide theair in three passes thereacross. Top walls .29 and 3f! together withextensions of the side walls 2 form a passage for the gases leaving thebank of tubes l to pass into the top ends of the bank of gas conductingtubes 22. bottom of said bank of tubes 22.

The dust separator D is made about equal in width to the width of thebank of boiler tubes H (see Figure 2) so that the gases leaving theseparator and flowing toward the bank of boiler tubes will besubstantially uniformly distributed across the width of the bank whenentering said upper portion of the bank. The dust separator D hereinused for illustration comprises a multiplicity of similar dustseparating units in this case small cyclone separators, extendingsubstantially uniformly distributed across the width of separator D andare arranged for parallel paths of gas flow therethrough insubstantially equal resistances. The bottom tube sheet 2c is providedwith a multiplicity of holes into each of which is mounted one of thecyclone separating units 32.

Each separating unit 32 is provided with a COD- A gas offtake duct 3! isprovided at the heater section 35 with respect to gas flow. The bafileIS in Figure '3 now forms the rear wall of the boiler and also forms afront wall for a chamber containing the heat exchanger E which, in thisinstance, is an economizer. The

rear wall 38 of the chamber for economizer ,E extends downwardly to therear wall 39 of the dust separator D.

In operation of the apparatus shown by Figures 1 and 2, the gaseousproducts of combustion flow upwardly in the furnace A, thence across thetop of baffle 6, thence downwardly through superheater C while some ofthe gases may flow downwardly throu h the bypassbetween'bafiles J2 andI3, thence across the bottom V of the bank oi tubes H. In the preferredembodiment of my invention illustrated in Fig. .1 .it :Will he notedthat a large cross-flow area is presented to the gases so as to keep thevelocity relatively low. In this manner erosion of tube surface byabrasiveflyash entrained in the gases is held within tolerable limits.After having their temperature reduced to a point where oxidation of thedust collectors surface ceases to be a problem, the gases pass throughdust collector D wherein the gases are substantially separated from thefly ash. The clean combustion gases then how upwardly over the majorportion Wiof tube bank ,II by way-of a sinuous path defined by bafiles1.3a. The .flow

path over tube bank portion W is so proportioned that the velocity ofthe gases and consequently the heat transfer rate to the tube bank ishigh. Since the gases are substantially free of fly ash. abrasion of thetubes or tube cutting is considerably minimized or eliminated and yethigh heat transfer and high economy in heating surface is assured. Uponleaving the bank of tubes H the gases pass downwardly through the gastubes 22 of air heater E to be discharged through offtake 3|.

In Figure 3 where only the upper portion of the furnace is shown, thetype of firing may be different from that shown in Figure 1 in thatthere may be provided means for burning pulverized fuel in the lowerportion of the furnace, not shown. The products of combustion 'rise inthe furnace A, a portion of which 'pass' upwardly and diagonally acrossthe first superheater section 35. thence across the top of baflie thencedownwardly through the second section of superheater C, thence throughdust separator D, thence directly upwardly through the third superheatersection S and finally through the economizer E to be discharged throuhofftake 40.

If the dust separator D is placed beyond the elements of the steamgenerating unit with respect to the gas flow it will have a lowerresistance to gas flow than when it is placed ahead of certain elements,because of the increase in gas volume and temperature at the latterlocation. However, I take advantage of this fact and place the dustseparator in an advanced location with respect to gas flow,substantially following the first superheater surface and ahead of themain body of boiler convection surface and/or economizer and air heatersurf-ace. I use a dust separator of the type whose gas inlet preferablyapproximates the width of the heating surface with which the gases havelast contacted, that employs a multiplicity of similar dust separatingunits arranged for parallel paths of gas flow therethrough ofsubstantially equal resistance, that discharges the gases at asubstantially uniform rate over the entire cross section of its gasoutlet, and whose gas outlet approximately equals the width of theheating surface next following the separator.

This arrangement, together with the relatively high resistances throughthe separator units, has the effect of redistributing any unequal rateof flow of the gases occurring ahead of the separator. The gases leavingthe separator are then delivered to the subsequent surfaces insubstantially uniform distribution and rate of flow over the width ofsaid surface and will insure a more uniform and improved heat absorptionin these surfaces.

By so placing the dust separator, I establish new and useful purposesfor it in that it delivers substantially dust-free gases to thesubsequent elements of the heating surfaces and serves as aredistributor to deliver gases to said heating surfaces in substantiallyuniform distribution.

A further advantage of my new location of the separator is that thesubsequent heat absorbing surfaces will be kept relatively clean andsoot blowers may be dispensed with.

While I have shown and described the preferred embodiment of myinvention, it will be understood that changes in construction,combination and arrangement of parts may be made without departing fromthe spirit and scope of the invention as claimed.

What I claim is:

1. In a steam boiler comprising a furnace from which combustion gasesare discharged and boiler heating surface over which said combustiongases flow in heat exchange relationship, the combination of meansforming a first channel which includes a relatively small portion of theaforesaid boiler heating surface and which causes that included surfaceto present a relatively large flow area to the passage therethrough ofthe aforesaid combustion gases with resulting low gas flow velocity oversaid included small portion of boiler heating surface; means forming asecond channel which includes a remaining substantially larger portionof the aforesaid boiler heatin surface and which causes that surface topresent a. relatively small flow area to the passage therethrough of theaforesaid combustion gases with resulting high gas flow velocity oversaid included large portion of boiler heating surface, said largerheating surface portion being arranged in series to follow the smallheating surface portion with respect to direction of gas flow; and adust separator interposed between the smaller boiler heating surfaceportion and the larger boiler heating surface portion, said dustseparator comprising a multiplicity of similar dust separating unitssubstantially uniformly spaced across the width of the gas stream,whereby the gases with dust therein carried in leaving the low velocitysmaller boiler heating surface portion enter said dust separator wheresaid dust is removed therefrom and upon leaving the separator in acleaned state flow over the said larger boiler heating surface portionat high velocity without damage to that surface.

2. In a steam boiler comprising a furnace from which combustion gasesare discharged and fluid heating surface over which said combustiongases flow in heat exchange relationship, the combination of meansforming a first channel which includes a relatively small portion of theaforesaid fluid heating surface and which causes that included surfaceto present a relatively large flow area to the passage therethrough ofthe aforesaid combustion gases with resulting low gas flow velocity oversaid included small portion of fluid heating surface; means forming asecond channel which includes a remaining substantially larger portionof the aforesaid fluid heating surface and which causes that surface topresent a relatively small flow area to the passage therethrough of theaforesaid combustion gases with resulting high gas flow velocity oversaid included large portion of fluid heating surface, said largerheating surface portion being arranged in series to follow the smallheating surface portion with respect to direction of gas flow; and adust separator interposed between the smaller fluid heating surfaceportion and the larger fluid heating surface portion, said dustseparator comprising a multiplicity of similar dust separating unitssubstantially uniformly spaced across the width of the gas stream,whereby the gases with dust therein carried in leaving the low velocitysmaller fluid heating surface portion enter said dust separator wheresaid dust is removed therefrom and upon leaving the separator in acleaned state flow over the said larger fluid heating surface portion athigh velocity without damage to that surface.

WILBUR H. ARMAC OST.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,943,949 Coghlan et al Jan. 16,1934 1,972,143 Gordon Sept. 4, 1934 1,972,893 Langvand Sept. 11, 19342,065,554 Beers Dec. 29, 1936 2,158,509 Kuhner May 16, 1939 2,189,234Wagner Feb. 6, 1940 2,213,052 Rosencrants et a1. Aug. 27, 1940 2,263,433Allen Nov. 18, 1941 2,391,860 Badenhausen Jan. 1, 1946 2,399,509 RichApr. 30, 1946

